Information relating to eye movement and eye position is useful for the diagnosis of many neurological conditions, such as dyslexia. A number of devices for obtaining such data have been described, many of which include eye position sensors based on variations of the Purkinje eye tracker, wherein a light beam is applied to each eye and the light reflected from the eyes is used to determine eye position. In a device for measuring eye position described in U.S. Pat. No. 4,889,422, issued Dec. 26, 1989 to Pavlidis, a frame is provided for holding a subject's head, to prevent relative movement between the head and eye position sensors. U.S. Pat. No. 5,070,883, issued Dec. 10, 1991 to Kasahara, relates to an eye movement detecting apparatus to be worn on the head of an individual being tested, to overcome the problem of relative movement between eye position sensors and the head. U.S. Pat. No. 5,305,764, issued Apr. 26, 1994 to Yamada et al., describes a device for measuring eye and head movement of a subject, so that the line-of-sight of an individual may be detected. Further devices are described in U.S. Pat. Nos. 4,373,787, issued Feb. 15, 1983 to Crane, and No. 4,102,564, issued Jul. 25, 1978 to Michael.
The above-mentioned prior art devices are similar in that they provide precise information regarding the position or movement of the eyes themselves. As these devices rely on delicate and sensitive eye position detectors to provide the information, they are complex, and the delicacy of the detectors limits their portability.
Diagnosis of some neurological disorders may not require detailed information regarding eye position. Attention-deficit hyperactivity disorder (ADHD) is one such neurological condition, characterized by inattentiveness, impulsiveness, and hyperactivity. In the diagnosis of ADHD, data relating simply to eye movement would suffice and, in such cases, the above-mentioned prior art devices are not appropriate owing to their complexity of construction and usability.
Moreover, the diagnosis of ADHD, as with any neurological disorder, is ideally carried out with young children, so that corrective measures can begin at an early age. To do this, it would be most advantageous to have a device which could be both portable and inexpensive so that it could be taken to schools to screen children and operated by school personnel after minimal training. However, as mentioned above, existing instrumentation available to test eye movement is usually very expensive, not portable, and difficult to use.